(57) A method for analyzing the fouling tendency of a bottoms slurry in a fluidized catalytic cracking unit, the method comprising the following steps:

(a) subjecting a sample of the bottoms slurry to a selected increased pressure above atmospheric pressure and to a selected temperature corresponding to a bottoms slurry temperature at which the bottoms slurry is proposed to be maintained in the fluidized catalytic cracking unit;

(b) maintaining the sample at the selected increased pressure and selected temperature for at least about two hours;

(c) cooling the sample and reducing the pressure;

(d) homogenizing the sample to produce a homogenized sample;

(e) extracting relatively higher molecular weight materials from the homogenized sampling and

(f) analyzing the extracted relatively higher molecular weight materials for at least one equality

wherein the steps (e) and (f) are carried out by:

(g) adding from about three to about five parts by weight of a solvent composition to one part by weight of a measured amount of the homogenized sample, thereby to form a liquid phase containing relatively low molecular weight slurry components and a precipitate phase containing relatively high molecular weight slurry material as a precipitate;

(h) separating out the precipitate; and

(i) analyzing the precipitate for at least one quality.